The present invention relates to novel chemical compounds, polymers made from such compounds and novel materials and products made from such compounds. Important use of the materials made from the invention is the manufacture of corneal contact lenses.
In recent years, corneal contact lenses have become more and more popular in the United States and throughout the world.
The great popularity of contact lenses is easily understood. One important reason is that such lenses provide perhaps the best possible manner of achieving optical correction for the eyes. The lenses fit directly over the eye, and when properly fitted, are easily retained in place. Problems common with spectacles, such as interference with peripheral vision, moving about on the head, discomfort, and the possibility of improper interpupilary distance, are easily overcome. Contact lenses provide cosmetic advantages and afford convenience and increased safety when used in diverse pursuits, particularly sporting events.
Now most commonly used contact lenses are generally sudivided into two types, so-called hard contact lenses, and soft contact lenses. Each type of lens has its own advantages, but each also includes certain disadvantages.
Referring first to the advantages of hard contact lenses, these lenses provide dimensional stability, so that the characteristics of an optical prescription will remain unchanged while the lens is in use in the eye. In some cases, the eye will actually conform to the contour of the lens over a period of time so as to improve the vision of the wearer. Moreover, hard contact lenses are relatively durable in relation to soft lenses.
While hard contact lenses have the above and other advantages, some patients find such lenses somewhat uncomfortable in use, and prefer the so-called soft contact lens. These lenses fall generally into three categories, namely lenses made from silicone rubber or like materials, lenses made from "HEMA" (hydroxyethylmethacrylate) or so-called "hydrogel" lenses, and finally, lenses of the methylmethacrylate base type, modified by the addition of polymers such as cellulose acetate butyrate ("CAB"). Soft lenses readily conform to the eye and are quite comfortable in short term use. They are extremely thin as well as soft and pliable. However, they do not provide satisfactory oxygen transmissibility through the lens.
Referring now to the disadvantage of both soft and hard contact lenses, neither type of lens is able to be worn by a user over an extended period of time because both types of lenses are not enough permeable to the oxygen. As a result, the cornea is unable to "breathe" properly. Consequently, after a period of time, the cornea becomes irritated or perhaps even damaged. Moreover, the lenses sometime tend to adhere to the eye of the wearer after being in place for an unduly long period of time, and this can cause discomfort and even damage to the eye.
In view of the foregoing advantages of contact lenses, it would be even further advantageous if there were a contact lens that possessed the known advantages of machinability, dimensional stability, toughness and optical clarity, and which were also sufficiently oxygen permeable to be worn by a user for an extended period, such as for several days, weeks, or even months or more. Users of such lenses could wear them for extended periods and still feel comfortable; could have good vision and not risk injuring their eyes. Contact lenses which could be worn for an extended period would eliminate common problems with existing lenses.
The anticipated life of an extended duration contact lens would be lengthened considerably. This is because the requirement for handling would be very greatly reduced. More sturdy lenses, such as known types of hard lenses, are not susceptible to tearing or cracking, but can be scratched by frequent removal and insertion and cleaning, particularly if they are dropped occasionally. Losing the lenses is a realistic possibility which could be minimized substantially by having lenses which are removed weekly, or monthly, or at greater intervals.
Referring now to prior attempts to provide polymers with increased oxygen permeability; normally, most or all such known polymers have either been too dimensionally unstable for satisfactory use, or have had other disadvantages. For example, it is known to add significant amounts of additives normally intended to increase wettability. While such materials are helpful in proper amounts, using excess amounts thereof has often tended to cause proteinaceous matter to deposit on and impair the transparency of the inner surface of the lens.
While numerous attempts have been made to improve the oxygen permeability of both hard and soft contact lenses, the attempts have met with only limited success, particularly in thicker lens. Moreover, many soft lens material provides an environment which is highly suitable for bacterial growth, and this calls for sterilization procedures which in turn require the lenses to be handled frequently.
The present invention, therefore, is intended from the standpoint of an end use product to provide contact lens materials which are sufficiently oxygen permeable that they may be worn by the user on a greatly extended basis in relation to prior art lenses, which do not have the disadvantages associated with known prior art lenses intended for this purpose.
Referring now to its chemical aspects, the invention relates to the manufacture of copolymers of an acrylic or methacrylic material of a known type and novel, silicone substitute acrylic or methacrylic compounds so as to produce an oxygen permeable plastic material which is uniquely suitable for manufacturing novel corneal contact lenses as referred to above. The expression "copolymers" is sometimes used herein for simplicity in referring to a polymer which includes two principal comonomers, although such polymer may incidentally include one or more additional known monomers in minor amounts for purposes such as cross-linking, increasing the wettability of the final product, or otherwise.
The copolymer compositions and products made therefrom are improved over counterpart prior art compositions by reason of increased dimensional stability and improved gas permeability. Such novel compositions also retain or provide improvements in desirable prior art characteristics such as optical clarity, the ability to be cast, molded and machined, and compatability with chemically bonded, hydrophilic materials adapted to improve the wettability of the finished product.
Preferably, the compositions comprise high molecular weight polysiloxanylalkylesters of acrylic and methacrylic acids and other compositions as monomers, copolymerized with methacrylates or other esters of acrylic or methacrylic acids, vinyl carbazole, vinyl benzenes, vinyl pyrrolidinone and itaconate esters.
According to the invention, one comonomer (the "first" comonomer) is an acrylic or methacrylic ester silane, substituted with one or more highly substituted siloxanyl group. One such typical comonomer is bis(trimethylsiloxy)methylsiloxanylbis(trimethylsiloxy)methacryloxypropyls ilane which can be copolymerized with an alkyl acrylate or alkyl methacrylate, (the "second" comonomer), with this copolymer composition in turn being cross-linked to a slight degree by cross-linking agents, and preferably further modified by the addition of compounds intended to increase the wettability of the finished copolymer material. This basic polymerization of the novel comonomers with known comonomers occurs through a known double-bond polymerization mechanism.
A certain proportion, such as 10% to 60% of this compound is then polymerized with one or more or other second comonomer compounds having the same or similar acrylic or methacrylic ester portion, together with the minor amounts of cross-linking and wetting agents, referred to above.
One more aspect of the present invention relates to the method of making the so-called first or novel comonomers of the invention. According to this method, chlorosilanes are reacted with hydroxy derivatives of polysiloxanyl groups, in the presence of pyridine to bond released hydrochloric acid in the form of precipitated salt of pyridinium hydrochloride at low temperatures. The details of this method are brought out in other portions of the specification. In still another aspect, the invention relates to alternate methods of preparing the above or similar products. One alternate method comprises reacting others, mono-, di-, or methacryloxypropyltrichlorosilanes with an excess of pyridine and reacting the resulting intermediates with polysilanols pentamethyldisiloxanol, heptamethylisotrisiloxanol (3-hydroxyheptamethyltrisiloxane) and trimethylsilanol at about -50.degree. C.
A monomer is removed from these reaction mixtures by purification following removal of the low molecular weight materials with the reaction products being purified by washing with weak alkalies or like materials.
The novel comonomer compounds of the present invention can be represented by the following formulas: ##STR1## where n is an integer 1, 2 or 3. and by: ##STR2## where n is an integer 1, 2 or 3. and by: ##STR3## where n is an integer 1, 2 or 3.
In the alkyl or phenyl ester second principal comonomer, the alkyl group contains 1 to about 10 carbon atoms, (typically 1 to 6 carbon atoms) and the phenyl ester contains a singly vinyl benzene, divinyl benzenes, and itaconate esters.
One compound which may be used as the first principal comonomer of the present invention is bis(trimethylsiloxy)methylsiloxanyl bis(trimethylsiloxy)methacryloxypropylsilane: ##STR4## another compound is bis{bis(trimethylsiloxy)methylsiloxanyl}-trimethylsiloxymethacryloxypropyl silane: ##STR5## One more suitable compound is bis(trimethylsiloxy)methylsiloxanylmonopentamethyldisiloxanylmonotrimethyl siloxanylmethacryloxypropylsilane: ##STR6##
Representative known or second comonomers which may be employed in the practice of the invention include the following:
methyl acrylate, methyl methacrylate PA1 ethyl acrylate, ethyl methacrylate PA1 propyl acrylate, propyl methacrylate PA1 isopropyl acrylate, isopropyl methacrylate PA1 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate PA1 cyclohexyl acrylate, cyclohexyl methacrylate PA1 benzyl acrylate, benzyl methacrylate PA1 phenyl acrylate, phenyl methacrylate PA1 n-vinyl carbazole, n-vinyl pyrrolidinone PA1 3-hydroxy 2-naphtyl methacrylate PA1 ethyl vinyl benzene, divinyl benzenes PA1 dimethyl itaconate, diphenyl itaconate PA1 and dihexylitaconate. PA1 ethyleneglycoldimethacrylate PA1 diethyleneglycoldimethacrylate PA1 triethyleneglycoldimethacrylate PA1 tetraethyleneglycoldimethacrylate PA1 polyethyleneglycoldimethacrylate PA1 divinyl benezene PA1 tetramethyldisiloxanyldi(methylmethacrylate)
Cross-linking monomers include difunctional compounds such as:
and mixtures thereof.
The wetting agents include, but are not limited to:
acrylic acid
methacrylic acid
n-vinyl 2-pyrrolidine, and
hydroxyalkyl esters of acrylic and methacrylic acids,
and mixtures thereof.
In view of the shortcomings of prior art contact lenses and the compounds and compositions used in making them, it is an object of the present invention to provide novel monomers useful in making improved lens materials, improved polymer compositions made from such novel monomers, and improved lenses made from such polymers.
Another object of the invention is to provide novel silicone compounds used as components of polymerizable monomers.
And still another object is to provide highly branched or substituted siloxane materials for a variety of uses, including the manufacture of copolymers, terpolymers or other polymer incorporating such materials.
A still further object is to provide one or more compounds containing alkyl esters of acrylic or methacrylic acids, and incorporating three polysiloxanylalkyl groups.
Another object is to provide an optically useful, novel polymeric material of increased oxygen permeability with respect to prior art compounds.
And another object is to provide a composition which will make possible the manufacture of corneal contact lenses which can be worn for an extended time period while providing greatly increased comfort to the wearer.
Another object is to provide a polymeric contact lens material which is compatible with additives of known kinds used to provide other desirable end use properties.
A still further object is to provide a method of manufacturing copolymers incorporating the compositions made by the novel methods referred to above .